There are known a wide variety of applications in which it is desired to pump a fluid and where conventional sources of energy for driving a conventional pump are not available or are uneconomical. An example of such applications is a conventional solar water heater wherein water circulation therethrough is effected by a thermo-syphon system and often involves aesthetic difficulties, or by an electric pump which involves considerable expense, requires thermostatic control and renders the system dependent on the continuous supply of electrical current. Another example is the pumping of liquids such as oil or gas at remote locations where conventional energy sources are not available and where an extremely long maintenance-free lifetime is of primary importance.
A number of heat operated pumps have been proposed. One such proposal is found in U.S. Pat. No. 3,937,599 which shows a thermally-operated motor comprising a flexible membrane connected to a distributor which alternatively couples the volume adjacent one side of the membrane to a source of vapour and to a condenser.
The device shown in U.S. Pat. No. 3,937,599 is relatively complicated, involving a large number of interacting moving parts. It would thus appear that the proposed device would require careful and timely maintenance to remain in operation.
The present invention seeks to overcome the disadvantages of prior art heat-operated pumps exemplified by the disclosure in U.S. Pat. No. 3,937,599 to provide a pump which requires relatively little maintenance due to the fact that it comprises a relatively small number of moving parts.
There is thus provided in accordance with an embodiment of the invention a heat operated pump comprising:
a boiler containing a driving fluid; PA1 means for heating said driving fluid in said boiler; PA1 condenser means; PA1 a pumping chamber including a flexible partition sealingly disposed in said chamber to define first and second sealingly separated portions; PA1 first inlet means defining a communication passage from the interior of said boiler to said first portion; PA1 first exit means defining a communication passage between said first portion and said condenser means; PA1 second inlet means providing a uni-directional flowpath from a source of fluid to be pumped to said second portion; and PA1 second exit means providing a uni-directional flowpath from said second portion to a fluid utilization location; PA1 said pumping chamber, first exit means and flexible partition being configured together to define a valve permitting communication between said condenser means and said first portion only when the volume of said first portion exceeds a predetermined volume; PA1 said condenser being maintained at a pressure less than the pressure of said fluid at said second inlet means.